New Components Call for a Hardware Comparison of Receiver Architectures
High Frequency Electronics
By Todd Nelson, Linear Technology Corp.
The battle between superheterodyne radio architecture and direct conversion (homodyne or zero-IF) radio architecture goes back to the 1930s. Each has its advantages for particular types of equipment. Superheterodyne is popular in cellular base stations and direct conversion has proliferated in software-defined radio applications such as municipal radios. The simplicity of direct conversion hardware promises lower cost, lower power consumption and less board space than superheterodyne, which is attractive to cellular service providers. Yet the hardware simplicity is offset by the software complexity to deal with inherent problems of DC offset. This article will probe the perceptions and realities of the hardware differences, exploring the easy path and simply ignoring the software issues. The tsunami of data transmitted over cellular networks was brought on by tremendous advances in smart phones, tablets and other devices that access the Internet in these frequency bands. This has increased the technical requirements, while pressuring suppliers to reduce costs. Modern base stations take many forms—from traditional racks to smaller units operating on just a few Watts of power. The circuitry required to support multiple channels in tiny base station form factors assume a variety of approaches to integration. With recent developments, just how significant is the difference between superheterodyne hardware and direct conversion hardware?
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